Electrochemical carbon dioxide reduction is a potential pathway for sustainable production of fuels and chemicals. However, the detailed catalytic mechanism in cells using high-current gas diffusion electrodes remains uncertain. Here we use proton-transfer-reaction time-of-flight mass spectrometry (PTR–TOF–MS) to perform operando analysis of intermediates and products generated by electrochemical carbon dioxide reduction in gas-diffusion-electrode-based flow cells with copper-based electrocatalysts. PTR–TOF–MS allows for sensitive detection of C1–C4 minor and major intermediates and products, measurement of their 13C isotope composition and precise identification of onset potentials. We find that formaldehyde and acetaldehyde are not the major intermediates for formation of methanol and ethanol/ethylene, respectively, and that propionaldehyde reduction is on the major pathway for 1-propanol formation. Interestingly, the discrimination against 13C in the reaction products is substantially larger than for biological CO2 fixation in photosynthesis and Fischer–Tropsch synthesis of hydrocarbons.
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The data and analyses for the figures in the main part of the manuscript are openly available at https://doi.org/10.5281/zenodo.7047052. All data in the study are available from the corresponding authors upon reasonable request.
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This work was supported by the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme through the eCO2EP project operated by Cambridge Centre for Advanced Research and Education in Singapore (CARES) and the Berkeley Education Alliance for Research in Singapore (BEARS). We thank E. Hartungen of IONICON for valuable technical advice on the operation of the PTR-MS instrument.
The authors declare no competing interests.
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Supplementary Notes 1–5, Figs. 1–28 and Tables 1–10.
Supplementary Data 1
Atomic coordinates of intermediates and products used in DFT calculations.
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Ren, H., Kovalev, M., Weng, Z. et al. Operando proton-transfer-reaction time-of-flight mass spectrometry of carbon dioxide reduction electrocatalysis. Nat Catal 5, 1169–1179 (2022). https://doi.org/10.1038/s41929-022-00891-3
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